The LOFT
A speaker’s level of proficiency in a language (A1, A2, B1, B2, C1, C2) are specified and organised by the Common European Framework of Reference for Languages (CEFR https://www.coe.int/en/web/common-european-framework-reference-languages/table-1-cefr-3.3-common-reference-levels-global-scale ) which determines the linguistic skills of a speaker in every level.
A1-A2
The speaker can interact in a simple way on everyday or familiar matters and personal details.
B1-B2
The speaker can adequately interact spontaneously and rather fluently on a range of subjects and argue both in written and oral form on more complex issues of interest or more abstract.
C1-C2
The speaker can understand at ease virtually everything or wide range of topics, can speak and write in a fluent and genre corresponding way in scientific/academic, professional and social situations.